1. Field of the Invention
This invention relates to electrostatic discharge devices, and in particular to a device worn on the heel of an operator wherein the device contains rivets which protrude from the bottom of the device to overcome soil build-up in the discharge of static electricity.
2. Description of the Related Art
In the process of contacting electronic components or parts to assemble into an electronics system, a major problem is the destruction of the parts by static electricity. A significant electrical potential difference between the part and an operator in contact with the part can cause the part to be damaged by the rapid transfer of static electricity. Due to the general existence of static electricity in the usual working environment and the expense of such electronic components, damage to these parts can easily occur and is highly undesirable.
The basic solution to the electrostatic discharge problem in the art is to provide a mechanism to an operator which electrically grounds the operator at a zero electrical potential. The electronic components to be in contact with the operator are also maintained at, or very close to, a zero electric potential. Therefore, there is generally no potential variation between the parts and the operator when they come into contact.
Examples of such electrical grounding devices are wrist strap devices worn by an operator at a work station where the operator is assembling an electronic device from parts. Because such devices have proved limiting in permitting the operator desired freedom of movement from a specific work station, a grounding device worn on the heel of the operator in contact with a special electrically grounded conductive floor was developed.
Examples of such heel grounding devices are produced by Westek of Arcadia, Calif.; the Westek Part No. M9902, a leg band that is an adjustable conductive stretch fabric with a snap with a wire (incorporating a one megohm resistor) leading from the leg band to the foot. The foot band is made of conductive rubber which makes contact with a grounded conductive floor. Westek also has shoe grounding device part Nos. MX9902M and MX9902F which tuck into the shoe and ground the operator through a 1 megohm resistor.
Also, SIMCO of Hatfield, PA produces reusable conductive heel grounders and sole grounders which provide continuous grounding of transient personnel to conductive flooring. Plastic Systems of Marlboro, MA is also a manufacturer of such devices.
A fundamental advantage of these prior art devices is that they permit the operator freedom of motion without being limited to a particular work-station.
However, a basic limitation has been encountered with prior art heel grounders. The grounders are comprised of an electrically conductive material which contacts an electrically grounded conductive floor. The devices gather soil from the conductive grounded flooring as the operator wearing the device (on his shoe) moves about. This is especially true when conductive rubber is used as worn on the heel of the operator, as the material is sticky and actually tends to attract soil from the floor as the operator moves along the floor. Even a floor that appears to be clean can have soil which builds up on the shoe of the operator. Such soil build up can actually occur within minutes. The non-electrically conducting soil acts as an insulation layer between the heel grounder and the grounded floor. As a result, electrical conductivity between the operator and the floor becomes reduced, ultimately rendering the device useless.
It would, therefore, be a great improvement in the art to have a heel grounding device which is resistant to the effects of soil accumulation.